Pertaining to Twitter. The etiquette of properly retweeting the words of others rather than trying to pass them off as your own by copy/pasting.
Good RTquette is shown by adding RT and the @username of the person whos words you want to pass on to your own followers (this can also be done automatically).
Poor RTquette is usually displayed by newcomers to Twitter who don't know better. These people should have the error of their ways explained to them.
However the worst type of offender are those that have been Twitter users for a long time, have amassed many thousands of followers, but repeatedly proffer enigmatic statements that they have read on and copied from the feeds of others.